Distance meter

ABSTRACT

The invention relates to a method ( 800 ), a sytem ( 100 ) and a device ( 102 ) for measuring the number of laps and/or the distance covered by a person during his/her performance. The invention relates particularly to a distance meter ( 102 ) to be worn by the user, which measures the distance covered by the object and comprises a magnetic sensor ( 212 ) for determining the direction of a magnetic field ( 304 ) external to the sensor relative to the sensor ( 212 ). The distance meter ( 102 ) to be worn by the user in accordance with the invention also comprises a counter ( 207 ), whose value is increased when the measured deviation of the magnetic field exceeds a preset limit, i.e. in the situation where a fitness trainer following a given track turns and starts moving into another direction on the track.

The invention relates to a distance meter. The invention relatesspecifically to a lap and distance counter for fitness trainers such asswimmers.

During their exercise, fitness trainers often move back and forth alonga given path, with the exercise target typically set as a covereddistance or number of laps. Fitness swimmers, for instance, typicallycarry out complete, successively repeated laps on a 25 or 50 m track ina swimming bath, sprinters run over a predetermined distance of a givenstretch and skaters or runners carry out several laps along an ovaltrack. Typical training comprises counting the covered distance ornumber of laps.

One manner of evaluating the performance and metering the distance iscounting the number of laps and multiplying the obtained number with thelength of the lap. Under exercising conditions, for instance, a fitnesstrainer will have to count the number of laps personally. This involvesthe problem that, while covering long distances or carrying out severallaps, the trainer has difficulties in finally remembering the number oflaps performed, especially if he/she has to concentrate on improvinge.g. a special technique at the same time, or if the performance haslasted a long time and the trainer is getting tired. In addition,especially in public swimming baths, there are many other personsexercising and other disturbing factors, which tend to affect thetrainer's concentration and counting of laps.

One solution to the problems mentioned above is provided by an abacus,for instance, in which the trainer shifts one bead for each performedlap. There are also known solutions, in which the fitness trainercarries a transceiver means, such as the ultrasonic solution disclosedby U.S. Pat. No. 5,136,621, in which the performance of one lap isregistered as the fitness trainer carrying the device passes by acertain control station. There are also various prior art solutionsbased on GPS means and acceleration sensors, which monitor the trainer'smovements in order to conclude the speed and the covered distance. U.S.Pat. No. 5,767,417 discloses a solution specially conceived for swimmerswith a view to measuring the covered distance and speed, comprisingmeans attached to the swimmer's body for measuring the water current. Inaddition, there is a prior art solution especially for swimmers, inwhich the swimmer hits a detector provided at the end of the pool, withhis hand, for instance, in order to mark a lap and thus to determine thecovered distance.

However, solutions of the kind above involve problems. Using an abacus,for instance, or touching a detector provided at the end of the track,such as a pool, requires free access for the swimmer all the way to theabacus or the detector, and his/her paying special attention to markingthe performed lap. What is more, for fitness swimmers, who make anorthodox U-turn at the end of the pool, it is even impossible to use anabacus or a detector to be touched. A further reason is that, on publicpremises, there may be mischief, involving intentional changes of thecounted number of laps during the use of an abacus or a detector to betouched. In addition, special transceiver means should be fitted inposition during the exercise, and this may be an impossible task in apublic skating rink or swimming bath, which is full of peopleexercising. Also, solutions based on GPS means and acceleration sensorsare costly and often inaccurate as well. Thus, for instance, with afitness trainer exercising at an indoor gym, there may be problems incommunicating between a GPS means and the satellite. Furthermore, thesolution based on measurement of the water current as disclosed by U.S.Pat. No. 5,767,417 is suitable only for swimmers, and it should also benoted that such a device, when used on public premises, might beanaesthetic and even interfere with many a fitness trainer'sperformances.

The purpose of the present invention is to provide an economical systemfor measuring the distance covered by a fitness trainer, which is easyto use and does not disturb him/her, allowing the prior art shortcomingsmentioned above to be reduced. The invention aims at bringing a solutionto the special issue of how to count the number of laps repeatedlycarried out by an object moving around a given track and how to measurethe distance covered without the trainer having to concentrate oncounting the number of laps or on using a device. Another purpose of theinvention is to conceive a solution allowing the number of performedlaps or the covered distance to be readily displayed to the trainingperson during and/or after the performance.

The goals of the invention are achieved as follows: the distance meterof the invention, which comprises means for measuring the direction ofan external magnetic field, is worn by the person, and one lap or trackside is marked as covered when a deviation of the magnetic sensor of thedistance meter relative to the direction of the external magnetic fieldmeasured by the sensor exceeds a set limit value, i.e. a situation wherethe person turns into another direction of movement on the track. Thedistance meter determines the covered distance with the aid of thenumber of laps/length of sides it has counted and the fed length of onesingle lap/side. In addition, the goals of the invention are achieved bybringing the distance meter in data transmission communication with atleast one other data processing device, such as, for instance, a devicefor measuring pulse data, and by storing the number of performed laps asa function of time.

The method of the invention for measuring the distance covered by aperson is characterised by

-   -   fastening on the person a magnetic sensor having substantially        stationary direction relative to the person,    -   monitoring any deviation of the magnetic sensor from a magnetic        field external to the sensor, and    -   counting the times the deviation of the magnetic sensor from the        external magnetic field exceeds a set limit value.

The distance meter of the invention for measuring the distance coveredby an object is characterised by the distance meter being worn by theperson and comprising a magnetic sensor for determining the direction ofthe magnetic sensor relative to a magnetic field external to the sensor,and also a counter and the distance meter to be worn by the user beingarranged to increase the meter value when the deviation of the magneticsensor from the external magnetic field exceeds a set limit value.

A number of preferred embodiments of the invention are defined in thedependent claims.

This patent application uses the following concepts, among other things:

-   -   In this application “a lap” denotes typically either a complete        lap, which is completed when the training person returns to        his/her starting point after having performed a complete lap or        half a lap around the track, such as, for instance, the length        of one stretch of a swimming pool. It should be noted that a        complete lap may be e.g. triangular, and then a lap may imply        the entire lap or one third of the entire lap, i.e. one side        length, or in the case of a square or oval track, a lap may        stand for the entire lap or one fourth of the lap, i.e. one side        length. It is obvious to those skilled in the art that various        combinations expressing the type of track can be implemented.    -   “A person” or object may be a fitness trainer, for instance,        such as a swimmer, a sprinter, a runner, a skater, a ski jumper,        a downhill racer, a canoeist or any other object, human or other        animal being, who moves along a track with his/her direction of        movement regularly reversed, such as e.g. a runner running along        an oval running track, or a swimmer swimming back and forth        along a swimming track in a swimming pool.    -   “Type of sport” or mode of use is the data describing the sport        to be performed which is fed into the distance meter to be worn        by the user, such as swimming, running or skating. With e.g.        swimming fed as type of sport into the distance meter, the        distance meter will be in “the swimming mode”, being especially        arranged to evaluate the results it has measured compared to the        determined type of sport.    -   “Magnetic field” is a magnetic field that is generated by a        source external to the distance meter and that can be measured        by the magnetic sensor of the distance meter, such as the        magnetic field of the earth. The magnetic field can also be        artificially generated by means of an electromagnet, for        instance.

The invention achieves considerable advantages over prior art solutions.The distance meter to be worn by the user in accordance with theinvention can be used without an external counter-means for accuratecounting of laps. The invention also allows for a lightweight and verysmall-sized meter, having a size even smaller than that of a matchbox,so that the meter does not interfere with the fitness trainer'sperformances and also is acceptable from a social point of view. Thedistance meter of the invention can also be made such that it can befastened to the person's garments by means of a simple fasteningmechanism, allowing the distance meter to be used with several garmentsand in different sports, and it is also easy to detach for laundry,change of garment or purchase of a new garment, for instance.

The fastening mechanism may be carried out by means of e.g. apress-stud, a Velcro tape or a suspender, allowing the distance meter tobe fastened directly to the garment, such as a belt, a pair of trousers,a pair of trunks or a headgear. The meter can also be equipped with aseparate belt or strap for fastening the meter. The fitness trainer'sgarment, such as a pair of trunks, may also have a pocket specificallydesigned for the distance meter, and the pocket can be transparent,allowing the fitness trainer to check his/her performance on the screenof a distance meter equipped with a display, directly through thegarment, without detaching the meter. With the pocket on the garmentdesigned for the meter, it is ensured that the meter is maintained inposition during the performance. The most reliable point for fasteningin terms of measurement techniques and the most advantageous point isfastening to the carrier's trousers, especially in the hip area, becausethe person's pelvic area remains stable compared to his hands or feet,for instance, during running, skating and swimming.

The invention has the special advantage of the magnetic sensor providedin the distance meter, allowing measurements of the direction of amagnetic field external to the meter, such as the magnetic field of theearth, relative to the meter. The magnetic sensor is preferably abiaxial magnetic sensor, but it can optionally be a triaxial magneticsensor. In addition, the distance meter can be equipped with controlmeans, such as press-studs, by means of which the meter can be switchedon and which can be used for feeding in advance the length of a lap or aside into the meter.

In one embodiment, the type of the track to be performed can also be fedinto the meter, such as e.g. an oval shape or a straight back and forthtrack, such as the track of a swimming pool, and the type of sport, suchas e.g. swimming, running or skating. The type of the track to beperformed can also be triangular, circular or have any other distinctgeometric pattern that can be illustrated in a plane. According to afurther embodiment of the invention, a limit value for a deviation ofthe magnetic sensor relative to the external magnetic field can be fedand set in the distance meter. Optionally, the user can conclude thelimit value by means of the fed track geometry without requiringactions.

In one embodiment, the distance meter of the invention can be arrangedin data transmission communication with another device, such as, forinstance, a pulse meter, and then the distance mater can deliver data ithas measured, such as the number of laps or the distance covered, to thepulse meter in the course of the sports performance. This allows thefitness trainer to check the number of laps and/or the distance coveredon a pulse meter at his/her wrist. In addition, decoding of the pulsemeter data may provide the pulse as a function of time and also as afunction of the covered distance. Optionally, the data collected by thedistance meter can be delivered also to other data processing devices,such as a display panel or a computer, for subsequent analysis, amongother purposes. The distance meter preferably comprises also a memoryunit, allowing delivery of data only after the sports performance hasended.

The data transmission communication can be performed e.g. with ashort-range radio link, such as Bluetooth technology, or by opticalmeans, such as e.g. by means of an IR transceiver. The data transmissioncommunication can be performed also by means of any other datatransmission method known by those skilled in the art, such as e.g. wiredata transmission technology.

The distance meter of the invention can also be equipped with a screenfor displaying e.g. the number of counted laps and/or the covereddistance and also for displaying fed data, instructions and other data,such as user interface data. The display is preferably an LCD display,but it may also be any other display known by those skilled in the art.

In one embodiment, the distance meter can be equipped also with meansfor detecting the meter mode, so that the meter detects when it is beingcarried by a user, the meter passing accordingly into standby state, forinstance, without requiring the user to take actions when fastening themeter to his/her garments. The means for detecting standby may be e.g. acapacitive sensor for measuring the permittivity of the environment, ora sensor measuring the temperature, the electric conductivity or themoisture. While the user is fastening the meter to his/her garment, anyof these variables may change under the effect of the user's presence,so that the meter may conclude that it is being carried and pass intostandby, and then measurements can be activated for example by pressingthe meter or any press button on the meter. In addition, a distancemeter especially devised for swimmers can be equipped with a moisturesensor allowing detection of the swimmer being in the water, and thenthe measurement unit is activated.

In a further embodiment, the distance meter of the invention can beequipped with a sensor detecting the fitness trainer's position. Thesensor detecting the position may be a separate sensor detecting theposition, or optionally a magnetic sensor with several axes. A distancemeter especially intended for swimmers or a distance meter in swimmingmode may detect when the swimmer is in swimming position and when he/sheis in vertical position. This allows erroneous counting of the laps dueto vertical rotation at the pool end to be avoided. Also, a sensordetecting the position may detect whether the swimmer is doingbackstroke or swimming on his/her stomach, thus preventing registeringof false information in situations where the swimmer switches frombutterfly to backstroke in the course of a lap.

The distance meter can also be equipped with a controller “learning” thelap cycle, comprising several modes for each sport and also allowing forthe geometric type and length of the fed lap and capable of evaluatingthe reliability of the performance compared to any fed sport and trackdata. Thus, for instance, if the user has fed swimming as the type ofsport and 100 metres as the length of a track lap, it is unlikely thatone lap would be performed in less than 20 seconds; yet this is feasiblein skating on a 100 m. track. In one embodiment, the controller canmonitor the lap times performed by the trainer in different sports andinfer the reliability of the marked lap from this. The controller maythus reject the marking of a lap, or at least give the trainer a warningof this, in case the lap time seems impracticable. One of the reasonsfor this may be a wrong definition of the sport, of the length of thelap/side or the geometric pattern of the lap, or optionally it may bedue to the fact that the distance meter has been kept switched on atother times than during the sports performance, tending to cause“unnecessary” rotation.

In one embodiment, the controller may “average” the direction of themeasured magnetic field, and then any momentary deviation caused e.g. bya rotation or the detour of an obstacle in the course of the lap can beignored in the counting of the laps. In another embodiment of theinvention, the sampling frequency can also be changed depending on thedistance, the sport and/or the track. In long-distance swimming mode,for instance, and on a long track side, the direction of the magneticfield can be measured by using a longer interval (a smaller samplingfrequency) than in the case of a fast sport and/or a short track.

Also, the distance meter to be worn by the user in accordance with theinvention can be programmed before the sports performance starts to givean alarm when the preset number of laps or distance is covered. If, forinstance, a swimmer wishes to swim 1,000 metres in a 25 m pool, he canprogram the distance meter to give an alarm when 1,000 metres, 20 lapsor 40 side lengths are covered. The distance metre of the invention maygive an alarm by means of an acoustic signal, a light signal or avibration, for instance. Optionally the programming and/or alarm can beperformed together with another data processing device compatible withthe distance meter to be worn by the user in accordance with theinvention, such as a pulse meter, for instance.

The distance meter can be programmed with an electric identifier (ID)identifying the distance meter or the fitness trainer, and in that case,if a plurality of distance meters are at a close mutual distance, it canbe avoided that the data of different distance meters get mixed witheach other as data are transferred by means of other data processingdevices, for instance.

In its most straightforward embodiment, the distance meter of theinvention is set into measuring mode at the beginning of theperformance, and the measurement is terminated at the end of theperformance using a control button on the meter.

Preferred embodiments of the invention are explained in further detailbelow with reference to the accompanying drawings, in which

FIG. 1 shows an exemplified distance meter to be worn by the user and asystem for providing data transmission communication between thedistance meter to be worn by the user and a data processing device inaccordance with one embodiment of the invention,

FIG. 2 shows a block diagram of an exemplified distance meter to be wornby the user in accordance with one embodiment of the present invention,

FIG. 3 shows the operating mode of an exemplified distance meter to beworn by the user in accordance with one embodiment of the invention,

FIG. 4 shows the direction of a magnetic field measured by the distancemeter of the invention as a function of time in a swimming pool of FIG.3, with movement in accordance with one embodiment of the presentinvention,

FIG. 5 shows the direction of a magnetic field measured by the distancemeter of the invention as a function of time, while a fitness trailerequipped with the distance meter is moving along a square track inaccordance with one embodiment of the present invention,

FIG. 6 shows the direction of a magnetic field measured by the distancemeter of the invention as a function of time, while a fitness trailerequipped with the distance meter is moving along a triangular track inaccordance with one embodiment of the present invention,

FIG. 7 shows the direction of a magnetic field measured by the distancemeter of the invention as a function of time, while a fitness trailerequipped with the distance meter is moving along an oval track inaccordance with one embodiment of the present invention,

FIG. 8 shows an exemplified method for enabling the operation of thedistance meter in accordance with one embodiment of the presentinvention.

FIG. 1 illustrates an exemplified distance meter 102 of the presentinvention to be worn by a person 101 and also a system 100 for providingdata transmission communication 110 between the distance meter 102 and adata processing device 112 in accordance with one embodiment of thepresent invention. The distance meter is typically equipped with ascreen 104 for displaying the counted laps and the covered distance andcontrol data and other interface data to the user. The distance meter102 may also comprise one or more control buttons 106 for controllingthe operation of the distance meter and for feeding data. In addition,the distance meter 102 can be equipped with fastening means, such as asuspender 108, for fastening the distance meter to the exercising personor to his/her garment.

In one example, during or optionally after the performance, the distancemeter 102 of the invention can be in data transmission communication 110with another data transmission device, such as e.g. a computer or a dataprocessing device carried at the user's wrist. The data transmissionconnection 110 is most preferably carried out by means of a short-rangeradio link. In accordance with the invention, the distance meter 102 maybe in data transmission communication with e.g. a wristwatch 112collecting pulse data, allowing the fitness trainer to monitor the datacollected by the distance meter directly on the screen of his watch,during the performance, for instance. Typically, the distance meterstores the data it has collected also in its memory means, allowing datato be checked later and perhaps transferred to some other dataprocessing device, such as a computer, for instance. In an exemplifiedembodiment, the data of the distance meter and the means collectingpulse data can be monitored in combination, allowing e.g. the pulse tobe observed as a function of the distance, the number of laps and/ortime.

FIG. 2 shows a block diagram of an exemplified distance meter 102 to beworn by the user in accordance with the invention and also connectionsbetween any components of the distance meter. The components of thedistance meter 102 are preferably interconnected by a mother board 202or a similar connecting element. In one embodiment, the mother board maycomprise a previously integrated unit performing e.g. arithmeticoperations, such as a processor 204, a memory unit 206, a counter 207and a clock 208. In addition, the distance meter typically comprises apower supply 210, preferably a battery.

A crucial component in the distance meter of the invention is a magneticsensor 210 for measuring the direction of an external magnetic field,the sensor being carried out e.g. by means of a biaxial magnetic sensorof HMC1022 type. The magnetic sensor may also have several axes. Thedistance meter also has control means 214, preferably press buttons, forcontrolling the operation of the distance meter and for feeding datainto the meter. The distance meter can also be equipped with a displayunit 216, such as an LCD display for displaying data. The distance meteralso typically comprises means 218 for data transmission, such as an IRtransmitter, an IR transceiver or a short-range radio link. Ashort-range radio link can be carried out by means of Blueboothtechniques, for instance. Data transmission between a pulse metercarried at the wrist and the distance meter is most preferably carriedout by means of a short-range radio link, however, data transmissione.g. between a computer and the distance meter can also be carried outwith wire data transmission techniques.

In a preferred embodiment of the invention, the distance meter to beworn by the user may comprise also a controller 220. The controller maycontrol the lap cycles relative to deviations in the measured magneticfield, relative to the time and relative to the length of a fed lap orside, and possibly to a fed sport type, and infer from this whether thedeviation has occurred within the limits of normal conditions, orwhether it is an erroneous interpretation, and then it either changes ordoes not change the value of the counter 207. The controller may alsolearn the fitness trainer's lap cycle by means of a special teachingmode, in which the fitness trainer programs the distance meter inteaching mode and performs the normal training performance around atrack, the controller storing data relating especially to the turningpoints, and in one embodiment, the controller may even suggest ageometric pattern as the track. After the teaching mode, the controllermay compare data of the consecutive laps with data of the lap performedduring the teaching mode, such as deviations from the magnetic field asa function of time. In one embodiment, the controller may also changethe sampling frequency to make it more consistent with the particularmeasuring situation.

The distance meter 102 of the invention may further comprise a sensor222 detecting the fitness trainer's position, such as e.g. a sensorbased on micro mechanic Bonded Silicon On Insulator (BSOI) techniques,or any other position-detecting sensor known by to those skilled in theart. The fitness trainer's position can be observed also by a magneticsensor 212, especially a triaxial magnetic sensor. A position-detectingsensor 222, or optionally 212, may detect when the fitness trainer is inswimming position and when he/she is in vertical position, so that, incase of the swimming mode or of a distance meter especially intended forswimmers, erroneous lap counting due to vertical rotation at the poolend can be avoided. The sensor 22 or 212 may also detect whether theswimmer is swimming on his stomach or on his back. In one embodiment,the distance meter 102 may comprise also means 224 for identifying theoperating mode of the meter, allowing detection of whether the meter iscarried or not carried by the user. In one embodiment, the distancemeter 102 may also comprise alarm means 226 for giving an alarm e.g.when a preset number of laps or distance is covered.

However, it should be noted that the distance meter 102 to be worn bythe user in accordance with the invention is exemplified, and that atleast part of the components are optional. In other words, the distancemeter to be carried by the user in accordance with the invention can beimplemented with a notably smaller number of components than those shownin FIG. 2.

FIG. 3 shows the operating situation 300 of an exemplified distancemeter carried by the user in one embodiment of the invention, where thefitness trainer 101 is a swimmer swimming back and forth in a swimmingpool 302. At a) the swimmer is swimming into a direction, where thesouth is on the rear left side and the north is on the front right siderelative to the swimmer's direction of movement. The magnetic sensorincluded in the distance meter 102 to be carried by the user inaccordance with the invention may thus infer the swimmer's direction ofmovement from the direction of the magnetic field 304 it has measured,in this case approx. 293°. At b), where the swimmer is returning in thesame pool, the determined swimming direction is approx. 113°.

In the case of FIG. 3, the measurement is most definite and accurate,given the reversed signs of the measured components indicating thedirection of the magnetic field at the turning point, where the swimmerresumes his incoming direction. Should the pool be positioned exactly inthe north-south direction or in the east-west direction, the sign ofonly one of the measured components would be reversed, and this wouldyet be a sufficient indicator of the swimmer having turned back in thepool. In fact, the reversal detection is most straightforward when thesign of at least one of the measured components describing the directionof the magnetic field is reversed.

FIG. 4 shows the direction of a magnetic field measured by the distancemeter of the invention as a function of time in the pool shown in FIG.3, with the user swimming back and forth along a straight track. In thecase shown in FIG. 3, the swimmer first swims along the track in adirection of about 290° for about 45 seconds, and then he resumes hisincoming direction of 113°, and continues swimming for about 45 seconds.The cycle is extremely distinct and the measurement accuracy is good.Especially if the distance meter averages the values describing thedirection of the magnetic field it has determined, any anomalies causedby slight meandering can be ignored. If the fitness trainer has fed thegeometric pattern of the track and the length of the side or lap intothe distance meter, the speed of said side or lap can be calculatedafter the side or lap has been counted. The average speed of longerintervals or optionally the fastest laps can also be determined.

However, it should be noted that, even if the sport shown in FIGS. 3 and4 is swimming, the operation of the distance meter of the invention isby no means restricted to swimming alone, the meter being equally wellapplicable to other sports as well, such as e.g. cycling, skating,running or paddling, involving regular repeated movement along a trackor lap.

FIG. 5 shows a square track and the direction of a magnetic fieldmeasured by the distance meter of the invention as a function of time,the fitness trainer equipped with the distance meter following a squaretrack, whose sides 1) and 3) extend in the south to north direction. Inthe exemplified case of FIG. 5, the fitness trainer starts theperformance at the intersection of sides 1) and 4), following first side1) to the north (either 0° or 360°, in this case 0°) for about 28seconds, and then turns to the west, into direction 270°, proceedingalong side 2). Then the fitness trainer turns to the south on the track,into the direction 180°, following side 3), and finally towards startingpoint, i.e. towards the intersection between side 4) and side 1),proceeding along side 4) towards the east in the direction 90°. In thiscase as well, the characteristic of the direction of the magnetic fieldas a function of time is distinct, i.e. the characteristic clearly showsthe turning points, allowing easy and accurate counting of the coverednumber of laps or sides.

FIG. 6 shows a triangular track and the direction of a magnetic fieldmeasured by the distance meter of the invention as a function of time,the fitness trainer equipped with the distance meter following thetriangular track, where the fitness trainer starts from the intersectionof sides 3) (east-west direction) and 1) and proceeds along side 1)towards the direction of about 330° for about 28 seconds, and then turnsalong side 2) to a direction of about 210° for about 28 seconds, andfinally turns to proceed along side 3) into a direction of about 90° forabout 28 seconds. It should be noted that having reached the startingpoint (intersection between sides 1) and 3)), the fitness trainer turnsvia the north to side 1), and then the characteristic describing thedirection of the magnetic field may make a momentary stop at 0°,however, owing to the controller, this will be ignored in the countingof laps. The fact whether the characteristic describing the direction ofthe magnetic field stops at 0° depends among other things on the fitnesstrainer's turning speed and the sampling frequency of the distance meterof the invention.

In one embodiment of the invention, the sampling frequency of thedistance meter can be changed. Especially on a long side or lap length,the sampling frequency can be set to a lower value, so that thedirection of the magnetic field can be detected only every other second,for instance. The sampling frequency can be changed without requiringactions by the user.

In the case illustrated by FIG. 6 as well, where the fitness trainerfollows a triangular track regularly, the characteristic of thedirection of the magnetic field measured by the distance meter of theinvention as a function of time is distinct, in other words, thecharacteristic distinctly shows the turning points, and hence the numberof covered laps or sides can be readily and accurately counted.

FIG. 7 illustrates an oval track and the direction of a magnetic fieldmeasured by the distance meter of the invention as a function of time,the fitness trainer equipped with the distance meter following an ovaltrack, where sides 1) and 3) are in the south-north direction and sides2) and 4) in the east-west direction. In the exemplified case, thefitness trainer starts from point A, proceeding first in parallel withside 1) towards the north into an approx. 0° direction for about 20seconds, and then he turns to proceed in parallel with side 2) into thedirection of about 270° for about 30 seconds. As the fitness trainer hascovered the stretch parallel with side 2), he/she further turns toproceed in parallel with side 3) to the south about 180° for about 20seconds, and eventually, before one complete lap is covered, along side4) to the east direction of about 90° for about 30 seconds.

It can be further noted that, when an oval track is regularly followed,the characteristic of the direction of the magnetic field measured bythe distance meter of the invention as a function of time is distinct,i.e. the characteristic distinctly shows the turning points, andconsequently, the covered number of laps or sides can be readily andaccurately counted.

FIG. 8 illustrates an exemplified method 800 for implementing theoperation of the distance meter carried by the user in one embodiment ofthe present invention, in which a magnetic sensor is initially fastenedto a person with substantially stationary direction relative to theperson. The operating mode of the distance meter can be identified instep 802 with the aid of a means for identifying the operating modeincluded in the distance meter, the value of the output signal of themeans being determined by the operating mode of the distance meter, i.e.by the fact whether the distance meter is being or not carried by theuser. In step 802 a, the distance meter can be switched in standby mode(ON), provided that the distance meter is worn by the user, or in step802 b it can be switched off from the standby mode (OFF), provided thatthe distance meter has been taken off, on the basis of the output of themeans for identifying the operating mode of the distance meter. However,steps 802, 802 a and 802 b are optional, and it should be noted that thestandby mode could also be switched on with a switch such as an ON/OFFswitch.

In the method of the invention, in step 804, track settings can be fedinto the distance meter, such as e.g. the geometric pattern of the trackto be followed (i.a. a straight, circular, triangular, square,rectangular, oval shape), the length of the lap and the length of theside. In step 804, a limit value for the deviation of the magneticsensor relative to an external magnetic field can be fed, or optionally,the limit value can be inferred from the fed geometric track pattern.The operating mode of the distance meter can be fed in step 806, butthis is not compulsory. The operating mode may describe e.g. the type ofsport to be performed, and it may be e.g. a running mode, a skating modeor a swimming mode. In one embodiment, a swimming mode, for instance,can be identified without requiring the user's actions, with the aid ofa sensor detecting the fitness trainer's position. The actual trainingarea can be detected in step 808 as the direction of the magnetic fieldas a function of time at a specific sampling frequency. The samplingfrequency may be fixed, or in one embodiment, it can be adjusted to thefed operating mode, the geometric track pattern and the length of thelap or the side, among other variables.

When there is a deviation of the direction of the measured magneticfield, step 810 can evaluate the reliability and permanence of thedeviation and also conclude whether the deviation was due to the fitnesstrainer's turning to another side on the track, for instance, or whetherthe deviation was a sudden deviation caused by an evasive movement, forinstance. If step 810 evaluated the deviation as an acceptable one, thevalue of the counter counting the number of laps or sides in increasedin step 812. This step may also calculate the covered distance with theaid of the fed track data and the counted laps. In one embodiment, step812 may deliver the number of counted laps and distance data over a datatransmission communication to another data processing device, such as adevice collecting pulse data, which the fitness trainer carries athis/her wrist. However, it should be noted that data can be transferredbetween an external data processing device and the distance metercarried by the user in accordance with the invention also during othersteps, and that the external data processing device may also be someother means collecting pulse data, such as a computer, for instance.

After step 812 or optionally after step 810, the method proceeds to step814 in order to decide whether the measurement should be continued. Ifthe user interrupts the measurement, for instance, the collecting ofmeasurement data can be ended in step 816, and the collected data can befiled in a file. If the measurement is continued, the process may returnto step 806, for instance. In one embodiment, and especially in the caseof a distance meter intended for the swimming mode or swimmers, theswimmer's position can be concluded in step 806, i.e. the fact whetherthe swimmer is in swimming position or in vertical position. If theswimmer is in swimming position, the measurement can be carried onnormally, but if the swimmer has remained resting in vertical positionat the end of the pool, the measurement will be carried on only when theswimmer has resumed his swimming position. The swimming position can bemonitored also during the other steps.

Only a number of embodiments of the invention have been described above.The principle of the invention can naturally be varied within the scopeof protection defined by the claims, regarding details of the embodimentand fields of application, for instance. In particular, it should benoted that the distance meter of the invention can be manufactured in asimplified version for a specific sport or track, such as a straighttrack for swimmers, and then it is not necessary to feed or set the typeof sport or track in the operating situation, but the entire measurementcan be carried out by activating the meter at the outset of theperformance and by stopping the meter at the end of the performance.

It should be further noted that, depending on the embodiment, the datatransmission between the distance meter of the invention and the dataprocessing device may be bi-directional, allowing the operation of thedistance meter to be controlled by means of said data processing device.The fitness trainer may feed data into the distance meter of theinvention in the course of the performance by means of a data processingdevice, such as a pulse meter carried at the fitness trainer's wrist.

1. A method (800) for measuring the distance covered by a person, characterised in fastening to the person (101) a magnetic sensor (212) with substantially stationary direction relative to the person, monitoring (808) any deviation of the magnetic sensor relative to the magnetic field (304) external to the sensor, and counting the times (812) the deviation of the magnetic sensor relative to the external magnetic field exceeds a set limit value.
 2. A method as defined in claim 1, characterised in that, before the performance starts, at least on of the following data is fed into the distance meter (102) reading the output of the magnetic sensor: type of sport, length of one lap or one side, data about the geometric pattern of the track and set value for the deviation of the magnetic sensor relative to an external magnetic field.
 3. A method as defined in claim 1, characterised in that the fitness trainer's position is also detected and a decision about continuing the measurement is made on the basis of the detected position and the fed type of sport.
 4. A method as defined in claim 1, characterised in that the distance covered is determined by the counted times and the fed length of a lap or a side.
 5. A method as defined in claim 1, characterised in that data are delivered from the distance meter (102) to at least one other data processing device (112).
 6. A distance meter (102) for measuring the distance covered by an object, characterised in that the distance meter (102) is a wearable distance meter, and that it comprises a magnetic sensor (212) for determining the direction of the magnetic sensor (212) relative to a magnetic field (304) external to the sensor (102), and also a counter (207), and that the wearable distance meter (102) is arranged to decrease the value of the counter (207) when the deviation of the magnetic sensor (212) relative to an external magnetic field (304) exceeds the set limit value.
 7. A distance meter as defined in claim 6, characterised in that the distance meter (102) comprises fastening means (108) for fastening the sensor with substantially stationary direction relative to the object and in that the fastening means is a press stud, a strap, a belt, a suspender (108) or a garment equipped with a pocket substantially adapted to the size and shape of the meter, such as a pair of trunks.
 8. A distance meter as defined in claim 6, characterised in that the distance meter (102) comprises control means (214, 216), such as a press button and a display for feeding at least one of the following data into the distance meter: type of sport, length of one lap or side, information about the geometric pattern of the track and a set value for the deviation of the magnetic sensor relative to an external magnetic field.
 9. A distance meter as defined in claim 6, characterised in that the distance meter (102) includes a sensor (222) for detecting the swimmer's swimming position and vertical position, respectively.
 10. A distance meter as defined in claim 6, characterised in that the distance meter (102) comprises a controller (220), which is arranged to evaluate the consistency of the measured lap cycle with at least one of the following: fed type of sport, length of lap, length of side, geometric pattern of the track, deviation of the magnetic sensor from the limit value of an external magnetic field and spent time.
 11. A distance meter as defined in claim 6, characterised in that the distance meter (102) is arranged in data transmission communication (110) with at least one other data processing device (112).
 12. A distance meter as defined in claim 11, characterised in that the data processing device is a computer, a display screen or a device measuring pulse data (112).
 13. A distance meter as defined in claim 6, characterised in that the distance meter (102) comprises a means (224) for detecting the operating mode of the wearable distance meter, the means allowing the conclusion whether the meter is being worn or not worn by the user.
 14. A distance meter as defined in claim 6, characterised in that the distance meter (102) is arranged to give an alarm when a preset distance or number of laps is covered. 